1. Field of the Invention
This invention relates to a non-aqueous electrolyte cell in which a unit cell is housed in an exterior packaging material comprised of a laminated film. More particularly, it relates to a non-aqueous electrolyte cell in which thermally fused portions of the exterior packaging material are collapsed.
2. Description of the Related Art
Recently, the tendency is towards cordlessness and portability of an electronic equipment, primarily exemplified by a notebook type personal computer, and small-sized lightweight portable electronic equipments, are being developed one after another. With the diversification of the electronic equipments, attempts are being made to reduce the thickness and the size of the secondary cells.
As the above-mentioned cells and the secondary cells, there is presented a polymer lithium ion secondary cell employing a high-polymer gel swollen with an electrolytic solution as the electrolyte.
Turning to the structure of the polymer lithium ion secondary cell, an active material comprised of LiCoO2 and zinc is layered on a positive electrode current collector comprised of a thin sheet of aluminum to constitute a positive electrode. On a negative electrode current collector is layered an active material comprised of, for example, carbon, coke, graphite, etc, to constitute a negative electrode. There is interposed, between the negative and positive current collectors, a separator which is a thin porous film composed of polypropylene or polyethylene. A high-molecular gel electrolyte, such as polyacrylonitrile (PAN), polyethylene oxide (PEO) or polyvinylidene fluoride (PVDF), is charged between these electrodes and the separator to provide an overall sandwich structure.
The unit cell of the sandwich structure is packaged by an exterior packaging material, as a sealing vessel, comprised of a soft metal film, such as an aluminum foil, and a plastic film, such as a film of nylon, polyethylene, polypropylene or polyethylene terephthalate.
In the non-aqueous electrolyte cell, in which the unit cell is packaged by the above-described exterior packaging material, the rim portion of the exterior packaging material is hermetically sealed by heat fusion when housing the unit cell therein. This heat-fused portion of the exterior packaging material is indispensable in view of water-proofing of the non-aqueous electrolyte cell and has at least a width of 5 mm.
Thus, in the non-aqueous electrolyte cell, the size of the unit cell plus the size of the heat-fused portion of the exterior packaging material represents the overall size of the cell. Thus, in the non-aqueous electrolyte cell, it has been difficult to reduce the outer size of the cell, in particular the projection area thereof in an electronic equipment from the planar direction.
It is therefore an object of the present invention to provide a non-aqueous electrolyte cell the projection area of which in the portable size electronic equipment can be reduced.
According to the present invention, there is provided a non-aqueous electrolyte cell in which a unit cell is housed in an exterior packaging material of a laminated film, formed with a spacing by deep drawing, and in which electrode terminal leads electrically connected to respective electrodes of the unit cell are led out to outside from the inside of the exterior packaging material, wherein the exterior packaging material is heat-fused around the spacing formed by deep drawing, with the heat-fused portion of the exterior packaging material being folded on itself except the heat-fused portion of the exterior packaging material from which are led out the electrode terminal leads.
With the non-aqueous electrolyte cell of the present invention, the folded portion of the exterior packaging material is immobilized by an adhesive transfer tape.
With the non-aqueous electrolyte cell of the present invention, the heat-fused exterior packaging material is folded on itself to reduce the size of the cell as seen from the planar side of the cell.
Also, with the non-aqueous electrolyte cell of the present invention, in which the folded exterior packaging material is immobilized with an adhesive transfer tape, it is possible to maintain the reduced outer size over protracted time.